1. Field of the Invention
The present invention relates to a switching arrangement for a reversible ratchet-type wrench to provide reliable ratcheting and to allow easy assembly and manufacture.
2. Description of the Related Art
Several factors are considered in designing wrenches and spanners, including improving the torque-bearing capacity, providing as many teeth as possible for the drive member, and providing an easy-to-manufacture structure. U.S. Pat. No. 2,957,377 issued to Hare on Oct. 25, 1960 discloses a reversible ratchet type wrench comprising a body 10 having a handle 11 and a head 12. A cap 39 and an annular wall 44 are provided to upper side and lower side of the head 12, respectively. Yet, this increases the assembly time and the manufacture cost and adversely affects the appearance. A shifting lever 35 is retained in place by a spring 33 that is located in a cylindrical opening 34. Nevertheless, formation of the cylindrical opening 34 that extends upward at an incline is relatively difficult. In addition, formation of the cavity 16 having converging straight sides 17, 18 which diverge in the direction of the periphery of rotatable member 14 requires expensive and accurate computer-numeric-control (CNC), which further results in an increase in the cost together with a low production rate. This is why such a reversible ratchet type wrench is hardly seen in the market.
FIGS. 13 and 14 illustrate another conventional ratchet type wrench comprising a handle 12xe2x80x2 and a head 11xe2x80x2. The head 11xe2x80x2 is machined to form four consecutive compartments for receiving the drive member 20xe2x80x2, the pawl 30xe2x80x2 and the shifting lever 40xe2x80x2, wherein three of the compartments can be formed by cutting, yet the remaining one must be machined by CNC. Further, the resultant head structure is relatively weak and thus has a poor torque-bearing capacity. In addition, the movement of the pawl 30xe2x80x2 for changing ratcheting direction is found unreliable, as it is achieved via transmission of the hook end 442xe2x80x2 of a spring 44xe2x80x2 attached to the shifting lever 40xe2x80x2.
FIG. 15 of the drawings illustrates a conventional wrench of the type having a handle Bxe2x80x2 and a head in which a drive member Axe2x80x2 is rotatably received. A pawl Dxe2x80x2 is slidably received in a transverse through-hole Cxe2x80x2 in a web between the handle Bxe2x80x2 and the head. However, an end of the pawl Dxe2x80x2 extends beyond the transverse through-hole Cxe2x80x2 and thus adversely affects operation of the wrench when used in a limited space. A two-pawl type wrench was proposed to solve this problem. As illustrated in FIGS. 16 through 18, the two-pawl type wrench includes a handle 1xe2x80x2 and a head 11xe2x80x2 extended from the handle 1xe2x80x2. A drive member 2xe2x80x2 is rotatably received in the head 11xe2x80x2, a receptacle 121xe2x80x2 is defined in a web 12xe2x80x2 between the handle 1xe2x80x2 and the head 11xe2x80x2, and a spring-biased switch member 4xe2x80x2 is mounted in a cavity 13xe2x80x2 in the web 12xe2x80x2. Two spaced pawls 3xe2x80x2 are received in the receptacle 121xe2x80x2 and are biased by two springs 6xe2x80x2, respectively. A threaded end cap 5xe2x80x2 is engaged with a threaded outer end of the receptacle 121xe2x80x2 to enclose the pawls 3xe2x80x2 and springs 6xe2x80x2. As illustrated in FIGS. 17 and 18, the switch member 4xe2x80x2 is turned to bias one of the pawls 3xe2x80x2 to engage its teeth 31xe2x80x2 with the drive member 2xe2x80x2 to thereby change the ratcheting direction of the wrench. However, it was found that the switch member 4xe2x80x2 cannot be reliably retained in place and thus tends to disengage from the cavity 13xe2x80x2. In addition, the pawl 3xe2x80x2 engaged with the drive member 2xe2x80x2 is not engaged with an inner longitudinal wall that defines the transverse through-hole and that faces the drive member 2xe2x80x2. As a result, the torque-bearing capacity of the wrench is poor. Furthermore, the outer pawl 3xe2x80x2 (FIGS. 17 and 18) tends to be stuck when the threaded end cap 5xe2x80x2 is mounted too close to the switch member 4xe2x80x2. To the contrary, if the threaded end cap 5xe2x80x2 is too far away from the switch member 4xe2x80x2, the pawl 3xe2x80x2 cannot be firmly engaged with the drive member 2xe2x80x2. Further, the threaded end cap 5xe2x80x2 tends to be disengaged from the drive member 2xe2x80x2, as the former is in threading engagement with the threaded outer end of the receptacle 121xe2x80x2.
FIGS. 19 through 21 illustrate another conventional wrench having a substantially V-shape transverse through-hole 25xe2x80x2 in a web between a handle 20xe2x80x2 and a head 21xe2x80x2 thereof. The head 21xe2x80x2 includes a compartment in which a drive member 22xe2x80x2 is rotatably received. A spring-biased pawl 23xe2x80x2 is received in each limb of the V-shape transverse through-hole 25xe2x80x2. A switch member 30xe2x80x2 includes a stem 35xe2x80x2 pivotally received in a cavity 24xe2x80x2 in the web and a thumb-piece 32xe2x80x2 extending from the stem 35xe2x80x2 for manual operation, thereby switching the switch member 30xe2x80x2 between two positions corresponding to two opposite ratcheting direction of the wrench. The thumb piece 32xe2x80x2 of the switch member 30xe2x80x2 includes a downwardly facing receptacle 36xe2x80x2 (FIG. 21) for receiving a spring 37xe2x80x2 and a ball 38xe2x80x2 that is biased by the spring 37xe2x80x2 to be positioned in one of two positioning recesses 281xe2x80x2 (FIG. 20) in a sector-like recessed area 28xe2x80x2 (FIG. 19) of the web. The switch member 30xe2x80x2 may be retained in place reliably. However, a C-clip 33xe2x80x2 is required for mounting the switch member 30xe2x80x2 in place, which adversely affects the aesthetically pleasing effect. In addition, processing of the sector-like recessed area 28xe2x80x2 in the web and the V-shape transverse through-hole 25xe2x80x2 is difficult. Mounting of the switch member 30xe2x80x2 as well as the pawl 23xe2x80x2 and associated springs 26xe2x80x2 and threaded end caps 27xe2x80x2 are troublesome and time-consuming. The sector-like recessed area 28xe2x80x2 in the web results in an increase in the overall thickness of the wrench, which limits application of the wrench in limited spaces. The torque-bearing capacity was found poor, as only a portion of the pawl 23xe2x80x2 meshed with the drive member 22xe2x80x2 was supported by the inner wall of the V-shape transverse through-hole 25xe2x80x2, as shown in FIG. 20.
In accordance with the present invention, a reversible ratchet type wrench comprises:
a handle;
a head extended from the handle and including a hole, the handle comprising a transverse receptacle communicated with the hole, the transverse receptacle comprising an inner longitudinal wall that faces the hole of the head, the handle further comprising a cavity that communicates with the transverse receptacle;
a drive member rotatably mounted in the hole of the head, the drive member including a plurality of teeth formed on an outer periphery thereof;
two pawls mounted in the transverse receptacle in a spaced manner and each including a first side with a plurality of teeth for releasably engaging with the teeth of the drive member and a second side abutting against the inner longitudinal wall of the transverse receptacle;
a switch member including a turn-piece for manual operation, the switch member being rotatably mounted in the cavity of the handle and comprising an actuating portion for selectively moving one of the pawls to a position not engaging with the teeth of the drive member, the switch member further comprising two support portions for selectively supporting a portion of the other pawl that disengages from the inner longitudinal wall of the transverse receptacle, thereby supporting the other pawl that engages with the teeth of the drive member; and
means for biasing the teeth of the pawls to engage with the teeth of the drive member, respectively.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.